Remove the speaker covers. Pull gently from both sides of the speaker until the cover pops free of the speaker.
Use the upholstery attachment of the vacuum to thoroughly vacuum the covers.
Fill the bathtub with warm soapy water and swish the speaker covers around in the soapy water.
Drain the bathtub. Run the shower with warm water and hold the speaker covers in the spray to rinse the soap from the covers.
Stand the speaker covers in the tub overnight to dry.
Return the speaker covers to the speakers. Make sure they're securely snapped into place.